<!DOCTYPE html>
<html lang='en'>

<head>
  <meta charset='UTF-8'>
  <meta name='viewport' content='width=device-width, initial-scale=1.0'>
  <title></title>
  <script type='text/javascript' src='js/vue.js'></script>
</head>

<body>
  <div id='app'>
    <div>
      <alert-box>456</alert-box>
      <alert-box>789</alert-box>
      <alert-box></alert-box>
    </div>
  </div>
  <script type='text/javascript'>
    Vue.component('alert-box', {
      template: `
        <div>
          <slot>123</slot>
        </div>
      `,
    })

    var vm = new Vue({
      el: '#app',
      data: {

      },
      methods: {

      }
    });
  </script>
</body>

</html>